1. Field of the Invention
The present invention relates to a composite conductor, production method thereof and a cable using the same conductor, and more particularly to a composite conductor used for a core wire or inner conductor (simply defined as xe2x80x9ccorexe2x80x9d hereinafter) of a small-diameter coaxial cable and/or an external or outer conductor (simply defined as xe2x80x9cexternal conductorxe2x80x9d hereinafter) and a production method thereof.
2. Description of the Related Art
The small-diameter coaxial cable equal to or less than 36 AWG (7-stranded wires) in conductor size is used for medical probe cable, an insertion cable in catheter, LCD harness cable and the like. Conventionally, a stranded conductor of Cu or Cu alloy of 50 xcexcm or less in diameter has been used.
In recent years, demand for multiple cores in case of medical probe cable, demand for reduction of the cable diameter in case of catheter insertion cable and demand for use of a single core in case of the LCD harness cable have been increased. That is, in these cables, cable material having a smaller diameter, excellent strength and flexing characteristic is demanded. Considering reduction of the diameter and economic performance, as the core, the single-wire cable is more favorable than the stranded cable. Therefore, instead of the stranded cable composed of the conventional core of Cu alloy having a short service life against flexings and insufficient strength and conductivity, the single-wire cable composed of alloy material (alloy cable material) having excellent strength and flexing resistance has been demanded.
As the conventional alloy wire material having a high strength, copper-metal fiber conductor in which metal such as Nb, Fe, Ag or the like is diffused in Cumatrix thereof (Cuxe2x80x94Nb base alloy, Cuxe2x80x94Nbxe2x80x94Cr base alloy, Cuxe2x80x94Nbxe2x80x94Zr base alloy, Cuxe2x80x94Ta base alloy, Cuxe2x80x94Fe base alloy, Cuxe2x80x94Ag base alloy, Cuxe2x80x94Cr base alloy) can be mentioned. Of the copper-metal fiber conductors, particularly, Cuxe2x80x94Nb base alloy, Cuxe2x80x94Fe base alloy and Cuxe2x80x94Ag base alloy are known to have excellent conductivity, processability and strength.
Further, as another conventional alloy wire material having a high strength and flexing resistance, the core is formed of Cuxe2x80x94Nb base alloy, Cuxe2x80x94Fe base alloy or Cuxe2x80x94Ag base alloy amoung the copper-metal fiber conductors and an external periphery of the core is coated with metal layer composed of Cu and unavoidable impurity, so that a composite cable having excellent conductivity, processability, strength and flexing resistance is produced (see Japanese Patent Application Laid-Open No. 6-290639).
However, because in the copper-metal fiberconductor, the metal fiber is exposed on the surface of the conductor and two kinds of the metals adjoin each other, if water or electrolyte exists, corrosion is likely to occur due to a difference of contact potential. Therefore, the copper-metal fiber conductor has a problem in corrosion resistance.
In the composite cable, the surface of the copper-metal fiber conductor is coated with Cu coating layer so as to prevent a corrosion by a difference of contact potential between different metals. However, if it is used in the atmosphere with the Cu coating layer as it is, it is discolored because of oxidation. If this discoloration is accelerated, copper oxide film is grown so that corrosion resistance reliability of the composite cable drops. For the reason, in the composite cable, a device for preventing discoloration and oxidation corresponding to the environment has been demanded. Generally, to improve corrosion resistance of the Cu cable, the surface of the Cu cable is coated with benzotriazole or plated with Sn, Ag or the like. However, in case where the composite cable is used for application for a small-diameter coaxial cable or the like, if the thickness of the plating layer is small, the Cu is partially exposed so that corrosion resistance reliability drops.
Further, the alloy wire material for use in the small-diameter coaxial cable is demanded to have not only excellent strength, flexing resistance and corrosion resistance but also excellent connectivity in terms of actual use. Here, of the connectivity, reliability (heat resistance) upon coupling at high temperatures by soldering or the like is an important factor.
Further, the alloy wire material used for these applications is demanded to have as small a diameter as possible and to be easy to produce, namely, processed to a long drawn wire. Therefore, this material is demanded to have an excellent processability (particularly, being drawn excellently).
Accordingly, the present invention intends to solve the above described problems and provide a composite conductor having excellent strength, flexing resistance and corrosion resistance and production method therefor and a cable using the same composite conductor.
To achieve the above object, according to a first aspect of the present invention, there is provided a composite conductor having a corrosion resistant layer 0.5 xcexcm or more thick constituted of Au, Ag, Sn, Ni, solder, Zn, Pd, Snxe2x80x94Ni alloy, Nixe2x80x94Co alloy, Nixe2x80x94P alloy, Nixe2x80x94Coxe2x80x94P alloy, Cuxe2x80x94Zn alloy, Snxe2x80x94Bi alloy, Snxe2x80x94Agxe2x80x94Cu alloy, Snxe2x80x94Cu alloy or Snxe2x80x94Zn alloy on an external periphery of a core of copper-metal fiber conductor.
According to a second aspect of the present invention, there is provided a composite conductor comprised of a metal coating layer of Cu or Cu alloy on an external periphery of a core of copper-metal fiber conductor and a corrosion resistant layer 0.5 xcexcm or more thick constituted of Au, Ag, Sn, Ni, solder, Zn, Pd, Snxe2x80x94Ni alloy, Nixe2x80x94Co alloy, Nixe2x80x94P alloy, Nixe2x80x94Coxe2x80x94P alloy, Cuxe2x80x94Zn alloy, Snxe2x80x94Bi alloy, Snxe2x80x94Agxe2x80x94Cu alloy, Snxe2x80x94Cu alloy or Snxe2x80x94Zn alloy on an external periphery of said metal coating layer.
According to a third aspect of the present invention, there is provided a composite conductor according to the first or second aspect wherein the copper-metal fiber conductor is formed of Cuxe2x80x94Nb base alloy, Cuxe2x80x94Ag base alloy or Cuxe2x80x94Fe base alloy.
According to a fourth aspect of the present invention, there is provided a composite conductor according to the third aspect wherein the Cuxe2x80x94Nb base alloy contains Nb of 3-35 mass %.
According to a fifth aspect of the present invention, there is provided a composite conductor according to the third aspect wherein the Cuxe2x80x94Ag base alloy contains Ag of 2-20 mass %.
With the above described structure, the corrosion resistant layer 0.5 xcexcm or more thick composed of Au, Ag, Sn, Ni, solder, Zn, Pd, Snxe2x80x94Ni alloy, Nixe2x80x94Co alloy, Nixe2x80x94P alloy, Nixe2x80x94Coxe2x80x94P alloy, Cuxe2x80x94Zn alloy, Snxe2x80x94Bi alloy, Snxe2x80x94Agxe2x80x94Cu alloy, Snxe2x80x94Cu alloy or Snxe2x80x94Zn alloy is provided on the external periphery of the cable, thereby ensuring an excellent corrosion resistance.
According to a sixth aspect of the present invention, there is provided a production method for the composite conductor comprising the steps of: applying area reduction processing on a cable of copper-metal fiber conductor; and in the middle of or after the area reduction processing, plating an external periphery of the cable with corrosion resistant layer 0.5 xcexcm or more thick of Au, Ag, Sn, Ni, solder, Zn, Pd, Snxe2x80x94Ni alloy, Nixe2x80x94Co alloy, Nixe2x80x94P alloy, Nixe2x80x94Coxe2x80x94P alloy, Cuxe2x80x94Zn alloy, Snxe2x80x94Bi alloy, Snxe2x80x94Agxe2x80x94Cu alloy, Snxe2x80x94Cu alloy or Snxe2x80x94Zn alloy.
According to a seventh aspect of the present invention, there is provided a production method for the composite conductor comprising the steps of: forming a cable of copper-metal fiber conductor having Cu or Cu alloy metal coating layer on an external periphery thereof; applying area reduction processing on the cable; and in the middle of or after the area reduction processing, plating an external periphery of the cable with corrosion resistant layer 0.5 xcexcm or more thick of Au, Ag, Sn, Ni, solder, Zn, Pd, Snxe2x80x94Ni alloy, Nixe2x80x94Co alloy, Nixe2x80x94P alloy, Nixe2x80x94Coxe2x80x94P alloy, Cuxe2x80x94Zn alloy, Snxe2x80x94Bi alloy, Snxe2x80x94Agxe2x80x94Cu alloy, Snxe2x80x94Cu alloy or Snxe2x80x94Zn alloy.
According to an eighth aspect of the present invention, there is provided a production method for the composite conductor comprising the steps of: applying area reduction processing on a cable of copper-metal fiber conductor; in the middle of the area reduction processing, forming Cu or Cu alloy metal coating layer on an external periphery of the cable; and after the metal coating layer is formed or the are a reduction processing is completed, plating an external periphery of the cable with corrosion resistant layer 0.5 xcexcm or more thick of Au, Ag, Sn, Ni, solder, Zn, Pd, Snxe2x80x94Ni alloy, Nixe2x80x94Co alloy, Nixe2x80x94P alloy, Nixe2x80x94Coxe2x80x94P alloy, Cuxe2x80x94Zn alloy, Snxe2x80x94Bi alloy, Snxe2x80x94Agxe2x80x94Cu alloy, Snxe2x80x94Cu alloy or Snxe2x80x94Zn alloy.
According to a ninth aspect of the present invention, there is provided a production method for the composite conductor comprising the steps of: applying area reduction processing on a cable of copper-metal fiber conductor; after the area reduction processing is completed, forming Cu or Cu alloy metal coating layer on an external periphery of the cable; and after the metal coating layer is formed, plating an external periphery of the cable with corrosion resistant layer 0.5 xcexcm or more thick of Au, Ag, Sn, Ni, solder, Zn, Pd, Snxe2x80x94Ni alloy, Nixe2x80x94Co alloy, Nixe2x80x94P alloy, Nixe2x80x94Coxe2x80x94P alloy, Cuxe2x80x94Zn alloy, Snxe2x80x94Bi alloy, Snxe2x80x94Agxe2x80x94Cu alloy, Snxe2x80x94Cu alloy or Snxe2x80x94Zn alloy.
According to a tenth aspect of the present invention, there is provided a production method for the composite conductor according to one of the sixth to ninth aspects wherein the corrosion resistant layer of Au, Sn or solder is formed according to electro-plating method or hot-dip plating method.
According to an eleventh aspect of the present invention, there is provided a production method for the composite conductor according to the sixth-ninth aspect wherein the corrosion resistant layer of Ag or Ni is formed according to electro-plating method.
With the above described methods, the corrosion resistant layer of Au, Ag, Sn, Ni, solder, Zn, Pd, Snxe2x80x94Ni alloy, Nixe2x80x94Co alloy, Nixe2x80x94P alloy, Nixe2x80x94Coxe2x80x94P alloy, Cuxe2x80x94Zn alloy, Snxe2x80x94Bi alloy, Snxe2x80x94Agxe2x80x94Cu alloy, Snxe2x80x94Cu alloy or Snxe2x80x94Zn alloy can be formed on the external periphery of the cable without modifying the existing equipment largely.
According to a twelfth aspect of the present invention, there is provided a cable having external conductors disposed around a core, wherein the core or the core and the external conductors are formed of single-wire cables each composed of composite conductor having a corrosion resistant layer 0.5 xcexcm or more thick constituted of Au, Ag, Sn, Ni, solder, Zn, Pd, Snxe2x80x94Ni alloy, Nixe2x80x94Co alloy, Nixe2x80x94P alloy, Nixe2x80x94Coxe2x80x94P alloy, Cuxe2x80x94Zn alloy, Snxe2x80x94Bi alloy, Snxe2x80x94Agxe2x80x94Cu alloy, Snxe2x80x94Cu alloy or Snxe2x80x94Zn alloy on an external periphery of a core of copper-metal fiber conductor.
According to a thirteenth aspect of the present invention, there is provided a cable having external conductors disposed around a core, wherein the core or the core and the external conductors are formed of single-wire cables made of composite conductor, each comprised of Cu or Cu alloy metal coating layer formed on an external periphery of the core of copper-metal fiber conductor and a corrosion resistant layer 0.5 xcexcm or more thick constituted of Au, Ag, Sn, Ni, solder, Zn, Pd, Snxe2x80x94Ni alloy, Nixe2x80x94Co alloy, Nixe2x80x94P alloy, Nixe2x80x94Coxe2x80x94P alloy, Cuxe2x80x94Zn alloy, Snxe2x80x94Bi alloy, Snxe2x80x94Agxe2x80x94Cu alloy, Snxe2x80x94Cu alloy or Snxe2x80x94Zn alloy formed on an external periphery of the metal coating layer.
With the above described structure, the core or the core and the external conductors are formed of single-wire material of composite conductor. Thus, connectivity such as solderability of soldering cable terminals with each other is excellent.
The reason why the numeric range is limited as described above will be described below.
The reason why the thickness of the corrosion resistant layer is 0.5 xcexcm or more is that if the thickness is less than 0.5 xcexcm, the corrosion resistance of the composite conductor is not sufficient.
The reason why the Nb content of the Cuxe2x80x94Nb base alloy is 3-35 mass % is that if the Nb content is less than 3 mass %, the service life against flexings is inferior and if the Nb content is 35 mass % or more, the wire is likely to be broken when it is drawn.
The reason why the Ag content of Cuxe2x80x94Ag base alloy is 2-20 mass % is that if the Ag content is less than 2 mass %, the service life against flexings is inferior and if the Ag content is 20 mass % or more, the wire is likely to be broken when it is drawn and further it becomes very expensive.
In the meantime, preferably, the diameter of the above described composite conductor is 0.1 mm or less.